Show failures when sending messages

This is useful for the spam checking where otherwise you don't
really know why your message has failed to send

Author: dbkr

src/components/structures/RoomView.js

@@ -738,6 +738,17 @@ module.exports = React.createClass({
     _getUnsentMessageError: function(room) {
         const unsentMessages = this._getUnsentMessages(room);
         if (!unsentMessages.length) return "";
+
+        if (
+            unsentMessages.length === 1 &&
+            unsentMessages[0].error &&
+            unsentMessages[0].error.data &&
+            unsentMessages[0].error.data.error &&
+            unsentMessages[0].error.name !== "UnknownDeviceError"
+        ) {
+            return unsentMessages[0].error.data.error;
+        }
+
         for (const event of unsentMessages) {
             if (!event.error || event.error.name !== "UnknownDeviceError") {
                 return _t("Some of your messages have not been sent.");